The present invention relates to a device and method for measuring an air permeability of an air permeable film or other paper or cardboard installed in a device for removing water vapor for dehumidification in a frame.
The air permeability test method using paper or cardboard specified by JIS P8117 is known as a conventional air permeability measurement method.
In this JIS P8117, an inner tube is fitted in an outer tube storing a sealing liquid so that the inner tube can slide up and down, an air passage extends from an air chamber formed inside the fitted inner tube to the bottom of the outer tube, and a sample clamping unit is provided between the air passage and an exhaust passage. In this method, oil was used as a sealing liquid.
However, when oil is used as a sealing liquid, oil mist is mixed in passing air. Essentially, the air permeability measurement is to measure permeability of air containing water vapor and oil mist is therefore a hindrance for the air permeability measurement. Then this oil mist is mixed in the passing air, the oil mist adheres onto a sample and blocks permeation and, as a result, it is undeniable that an error occurs in a measurement result.
Therefore, use of water as a sealing liquid can be thought for avoidance of an influence by the oil mist.
When water is used as a sealing liquid, water vapor generated by evaporation of the water is spread in passing air within the air chamber or the air passage.
Closer to the water surface, higher the vapor concentration. Therefore, the water vapor gradually flows into the air passage as the inner tube slides down, and humidity starts rising gradually from the start of the measurement. Because such humidity variation can be an error cause in the air permeability measurement, this humidity need be calculated to obtain humidity in the passing air as a requirement for air permeability evaluation.
The present invention is done to solve the above-mentioned problem of the conventional method. The bad influence of the oil mist can be avoided by using pure water in place of oil as a sealing liquid.
The subject is to provide the unit and method for measuring an air permeability that enable precise air permeability measurement by using water and seizing variations in vapor concentration.
In addition, a measurement under an influence of a difference between surface temperatures of a vapor exhaust port and a vapor supply port of a sample being measured and a measurement under an influence of an electrical charge on the sample being measured will be enabled.
To solve the aforementioned problem, the device for measuring an air permeability according to the present invention (claim 1) is:
a device installed in a constant temperature/humidity room wherein;
an inner tube having an opened bottom is fitted in an outer tube having an opened top and storing a sealing liquid so that the inner tube can slide up and down;
an air chamber is formed inside the fitted inner tube; pure water is used as said sealing liquid in the device for measuring an air permeability wherein a sample clamping unit is provided between an air passage extending from the air chamber to the bottom of the outer tube and an exhaust passage facing the air passage; and
a device for measuring humidity, a device for measuring a temperature, and an air supply port opened/closed by a solenoid valve are installed in the vicinity of the sample clamping unit in said air passage.
In this case, one embodiment (claim 2) shows that an exhaust fan is installed facing the exhaust passage.
The method for measuring an air permeability according to the present invention (claim 3) is;
a method for measuring an air permeability by using said device for measuring an air permeability comprising;
a primary process of measuring humidity wherein the inner tube is raised to a specific height while air is taken into the air chamber from the air supply port with an impermeable sample set in the sample clamping unit, then the inner tube is freed after the air supply port is closed and, in this state, humidity is measured using the device for measuring humidity;
a secondary process of measuring humidity wherein the inner tube is lifted up to a specific height while air is taken into the air chamber from the air supply port with a sample for measurement set in the sample clamping unit, then the inner tube is freed after the air supply port is closed and, in this state, humidity and a temperature are measured with the lapse of time using the devices for measuring humidity and a temperature; and
a process of measuring a drop time carried on simultaneously with the secondary process of measuring humidity wherein a time required for the inner tube to drop for a specific amount is measured and calculating an amount of moisture permeation by subtracting a value obtained from said secondary process of measuring humidity from a value obtained from said primary process of measuring humidity.
In this case, one embodiment (claim 4) shows that an exhaust process wherein exhaust air is exhausted by an exhaust fan from the air chamber through the air passage and the exhaust passage is provided as a preprocess for the primary and secondary processes of measuring humidity.
Embodiments of this method of measuring an air permeability, also include:
an embodiment (claim 5) showing that a perforated plate is provided in the vicinity of a sample to be measured in a vapor exhaust port of the sample, then this perforated plate and the sample are set in the sample clamping unit, and in this state, an air permeability is measured with a difference between temperatures on the surfaces of the vapor exhaust port and vapor supply port or while giving a temperature difference by using a feature that a temperature on the surface of the vapor exhaust port of the sample being measured is changed by heat transfer from the outer tube or other part through the thermal conductivity of the perforated plate;
another embodiment (claim 6) showing that the perforated plate was selected from a multiplicity of perforated plates having different thermal conduction speeds; and
another embodiment (claim 7) showing a measurement with the perforated plate grounded or ungrounded.